Telephone system



, No. 749,306. 'PATENTED JAN. 12, 1904.

\ A. D. T. LIBBY.

TELEPHONE SYSTEM.

APPLICATION FILED DEU. 3, 1902.

N0 MODEL.

i the talking-circuits.

lines, 'as well as in the ordinary type, to main- `ing of the wantedsubscribers.

UNITED STATES Patented January 12, 1904.

PATENT OFFICE.

l ALBION D. T. LIBBY,V OF CHICAGO, ILLINOIS, ASSIGNOR TO KELLOGGSVVITCHBOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A

CORPORATION OF ILLINOIS.

TELEPHONE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 749,306, dated January12, 1904. Application filed December 3, 1902. Serial No. 133,673. (Nomodel.)

4cut-off relays of` the lines are bridged across the same or otherwiseconnected with the talking-circuits, and are therefore actuated over It1s necessary 1n these tain the cut-off relays actuated during the call-The callingkeys are arranged to open the connection of the centralbattery with the lines at the time of ringing to prevent theringing-current from going back over the lines of the callingsubscribers, and thus proving an annoyance to them by causing noise intheir telephones. The cutting' off of the battery, however,unlessiauxiliary means are provided, denergizes'the cut-off Vrelays andprevents the de- One such means is to employ an auxiliary generator orgenerators which is normally disconnected `from the lines andcord-clrcuits, but which during ringing is temporarily connectedtherewith, and is arranged to hold up the said relays. This isobjectionable for several reasons, among which `maybe mentioned theeXtra expense involved in the cost and running of the eXtra generators,the additional space required for the installation,` and a greatercompl'ication throughout.

`My invention is designed to accomplish the desired result with muchless complication than heretofore and with greater economy andefficiency.

The invention is illustrated in the accompanying drawing, in which thefigure represents adiagram of two subscribers lines and thecentral-oiiice apparatus involved in establish-` ing connections forconversation.

Two line-clrcuits L and L are shown eX- office C. At the substation thesleeve line4 conductor 3 terminates in a hook-switch 4, which isnormally grounded through a signalingbell 5. A receiver 6 andtransmitter 7 are adapted to be connected in series between the lineconductors when the receiver is removed from the hook-switch 4, at whichtime also the grounded bell is disconnected from the conductor 3. Thisapparatus at the substation is intended merely to typify any of theusual common battery transmission sets, as it is evident that any othersuitable arrangement may be employed in so far as the features of myinvention are concerned.

At the central oiiice the line conductors 2 and?) terminate,respectively, in springs 8 and 9 of a cut-olf relay R, the normalContact of spring 8 being connected by conductor 10 with the winding ofthe line-relay R2, which is joined through the medium of conductor 11with the live pole of the charging-battery B and the other pole of whichis grounded. The

,normal contact of spring 9 of the cut-off relay is grounded, asindicated by the conductor 12. The line-relay R2 controls the localcircuit of the line-signal S, which in this instance is in the form of asmall incandescent lamp. Each line is also provided with ananswering-jack .I and with a suitable number of multiple jacks J2 andJ3, the tip and sleeve contacts of which are respectively connected bymeans of conductors 13 and 14 With the forward contacts of the springs 8and 9 of the cut-off relay R. The winding of this relay is bridgedbetween the said conductors 13 and 14, as shown.

The opcrators outfit comprises a plurality of cord-circuits,` oneonly-being shown, and which is provided with an answering-plug I and acalling-plug P2, each having tip and sleeve contacts adapted to registerwith the like contacts of the spring-j acks or connectionterminals ofthe lines, and the tip-contacts ofn which are connected together throughthe lnedium of the tip-strands t and t2 and theinterposed condenser c,while the sleeve-contacts are joined by the strands s and s2 and theinterposed condenser c2. From the tip and sleeve strand of theanswering-plug conductors 15 and 16 extend to the opposite poles of thebattery B, as shown, and each includes one of the differential windingsof the supervisory relay o1, which-is adapted to control through itsnormally open contacts the local circuit of the supervisory lamp S2,associated with the answering-plug P. The strands t2 and s2 of thecalling-plug P2 are likewise connected by means of conductors 17 and 18with the opposite poles of a second charging-battery B2, and, asbefore,these conductors include the differential windings of thesupervisory relay r2, which controls through its normally open contactsthe local circuit of the supervisory lamp S2, energized also from thebattery B2.

The operators receiver 19, the secondary of her-induction-coil 20, and acondenser c3 are adapted to be bridged between the two strands t2 and s2by means of the listening-springs 21 of a suitable listening and ringingkey. Her transmitter 22 and the primary of her induction-coil 20 areshown in a local circuit with a small battery B3; but it will beapparent that any other suitable source of current may be employed. Analternating-current ringing-generator 23 is employed to call the wantedsubscriber and is connected between the ground and the sleeve-spring 24of the ringing and listening key. A suitable non-induc tive resistance,which may be a lamp 25, is included in the ringing-circuit. The outercontact of the tip-spring24 of the ringingkey is connected byc0nductor26 with the battery-lead 112, extending to the ,live pole ofthe battery B2, and said conductor includes a suitable vretardation-coil27. The line L2 is provided with apparatus similar to that of the line Land which is designated by the corresponding reference characters.

rlhe operation is as follows: The subscriber A desiring a connectionwith the subscriber D takes up hisreceiver and closes the lineconductors 2 and 3 togetherA at the substation, thereby completing thepath for c urrent from the battery B over the conductor 11 through theline-relay R2, conductor 10, and thence over the tip line conductor 2and through the substation instruments and back to the cen'- tral ofliceover a sleeve line conductor 3 and thence through the grounded branch12. The line-relay responds to this current and closes the local circuitof the signal-lamp S, which is lighted to indicate the subscribers call,upon seeing which the operator inserts the answering-plug P of hercord-circuit in the answering-j ack J of the line. The insertion of thisplug closes a path for current from the battery B over both strands ands of the cord-circuit and the switchboard-conductors 13 and|14 oftheline and through the cut-olf relay R. This relay therefore operates todisconnect the vline-relay R2 to render the line-signal S inoperativeand to also connect the switchboard-section of the line with theexternal line-circuit, thus placing the line in condition forconversation. rlphe current now flows from the battery B through thesupervisory relay 7 and over the metallic line to the substation as wellas through the cut-0H relay R, with the result that the magnetic eectsthrough the coils of the relay fr are neutralized and the relay does notattract its armature and the local circuit of the supervisory lamp S2 isnot closed. Upon learning the connection desired by the callingsubscriber the line is tested by means of the tip of the calling-plugP2. If the line is busy, a cord-circuit similar to the one shown andconnected with the same batteries is inserted in one of the jacks of theline, so that all of the test-rings thereof and which are connected withthe sleeve sides of the line are thereby connected With the live pole ofthe battery B or B2. Upon touching the tip of the plug P2 to one of thetest-rings, therefore, a complete path for current is providedffrom thetest-terminals over the tip-strand t2 of the testing cord-circuit andthrough conductor 17 to ground. This varies the charge of poten- 'tialupon the operators condenser to such an extent as to cause a surge ofcurrent through her bridge and produces a click in her receiver. If theline is idle, however, the testrings are entirely insulated, s0 that nopath for current is completed when the line is tested and no click isreceived. Upon finding the line in this condition the plug P2 isinserted and the ringing-key 24 operated. rlhe operation of thisringing-key connects the alternating-current generator 23 between thesleeve-spring and ground, and the tip-spring is connected with theconductor 26, leading to the live pole of the battery B2 through theretardation-coil 27. At the same time the springs 24 open the strands ofthe cord-circuit through their normal contacts to prevent the passage ofthe ringing-current back over the cord-circuit and through theinstrument of the waiting calling subscriber. The severance of thiscircuit, however, does not deenergize the cut-off relay R of the line L2for the reason that steady current for maintaining the same operated isfurnished from the live pole of the battery B2 over the conductors 11uand 26 and thence through the switchboard-cable 13, the winding of thecut-off relay R, switchboard-cable 14, and thence over the sleeve-spring24 of the ringing-key and through the ringing-generator 23 to ground.The current iowing over this path is suiiicient to maintain the cut-0Erelay R operated during ringing, and at the same time theringing-current from the generator 23 is not shortcircuited through thispath by reason of the presence therein of the retardation-coil 27, whichserves to effectually prevent its passage IOO ITO

and to confine it toits intended path over the sleeve line conductor 3of the. line L2 and through the grounded signaling-bell 5 at thesubstation. After calling the subscriber and t 5 before his responsea'path for current is pro `vided from the battery B2 over the conductor18 andtlirough one winding of the supervisory relay r2 and thence overthe sleeve-strand of the cord-circuit, the sleeve-conductors 14 and 3 ofthe line L2, andthrough the bell 5 of the i substation to ground. Thisserves to unbalance the magnetic effects in the two coils of y relay r2and energizes the same to cause it to S3 associated with the plug P2,which is lighted to indicate the fact to the operator that the calledsubscriber has not yet responded. Upon the response of the Icalledsubscriber the i ground through the bell 5 `at the substation is -20removed, and the metallic circuit is completed for current from thebattery B2, with 'the attending result that the relay 1'? is renderedneutral, and the local circuit of the supervisory lamp S3 is4 opened toyextinguish the same. The subscribers are now in conversation, and thebatteries B and `B2 are furnishing current to the respective substationswith which they t are Aassociated for transmission purposes. Thewindings of the supervisory-relays r and r2 are preferably placed uponthe opposite ends oftheir cores or otherwise separated, so that althoughthe magnetic elfects produced by the steady current flowing therethrought during conversation areneutralized the magt .netic effects duetorapidly-varying voice-currents are not neutralized, but cause'suiiicientimpedance topi-event thevoice-currents from `being"slfiort-circuitedthrough the bridges of the cord-circuitin which they, together with thebatteries, arelocated.; i t t Although, the `electrical dimensions ofthe severaldevic'es lemployed are not of the essence of my invention andmay be varied considerably, good, results have beenobtained with animpedance-coi] 27 of two hundred and ninety ohms Aandthe other parts ofthe usual or desired dimensions. .It will be understood t that anyYsuitable ringing and listening key y may be provided, but preferablyone in which the `movement of `a single lever serves to si- Althoughbutone type of line-circuit has been described, I do, notdesire to soconfine the invention, but hold it tov include all the uses andapplications to which it; maybe found capable andrparticularly apply tothose line-circuits in which the cut-01T relays are energized by currentflowing over `a portion of thetalking-circuit.` t i y Itclaim---iA t iV- i 1. In a `telephone system, the combination witha telephone-line, ofa line-signaling device therefor, a cut-off relay for the line adaptedwhen actuated to render said line-signaling z device inoperative acord-circuit to estabclose' the local circuit of the supervisory lamp imultaneously operate the opposite springs.,`

lish connections with the line, a steady current source associated withsaid cord-circuit and adapted during a connection to furnish currentover a portion of the talking-circuit for the operation of said cut-0Hrelay, a ringing-generator adapted to be connected with the line to callthe subscriber located thereon, means to open the cord-circuit duringcalling to prevent the ringing-current from iowing back over the same,an auxiliary path for current completed from said source through saidcut-off relay during calling, and means in said auxiliary path to permitthe passage of steady current and to prevent the passage of theringing-current, substantially as described.

2. In a telephone system, the combination with a telephone-line, of aline-signaling device therefor, a cut-off relay for the line adaptedwhen actuated to render said line-signaling device inoperative, acord-circuit to establish connections with the line, a steady currentsource associated with said cord-circuit and adapted during a connectionto furnish current over a portion of the talking-circuit for theoperation of said cut-.off relay, a ringinggenerator-adapted to `beconnected with the line to call the subscriber located thereon, means toopen the cord-circuit during calling to prevent the ringing-current fromflowing back over the saine, an auxiliary Apath for current completedfrom `said source through said cut-ofi? .relay during calling,and aretardation-coil in said auxiliary-path toprevent the passage ofringing-current andyto permit the passage of steady current,substantially as described. i

, 3. In a telephone system, the combination with atelephone-line, ofzaline-signaling device therefor, a cut-ofi' relay for the line adaptedwhen actuated to render said line-signaling -device inoperative, acord-circuit to establish connections with the line, a steady currentsource connected therewith and adapted4 to furnish current over aportion of the talkingcircuit during a connection for the operation ofsaid cut-off relay, a ringing-generator adapted to be connected withtheline to call the subscriber located thereon, means-to open the normalconnection with said source during calling, an auxiliary path forcurrent completed from said source through. said cut-off relay duringcalling, and a retardation-coilin said auxiliary path, substantially asdescribed.

4. In a telephone system, the combination witha telephone-line, of aline-signal therefor,

`a cut-.off relay bridged between the line conductors and adapted whenactuated to'render the line-signal inoperative, a `cord-circuit toestablish connections with the line, `a source of steady currentbridged. across the cord-circuit andadapted during a connection :tofurnish current over the talking-circuit for the operation of saidcut-off relay, a ringing-generator adapted to be connected with thecordcircuit to call the wanted subscriber, the cordcircuit being openedbetween said source and the cut-off relay at the time of calling thesubscriber, an auxiliary path for current from 'the line-signalinoperative, a cord-circuit to 'establish connections with the line, asource of steady current bridged across the cord-cir- A cuit and'adapted during a connection to furnish current over the talking-circuitfor the operation ofs-aid cut-off relay, a ringing-generator, a keylocated in the cord-circuit between thel bridge containing said sourceand the calling-plug, said key being arranged to sever the cord-circuitwhen the ringing-generator is connected with the calling-plug, an

auxiliary path for current from said source completed by said key duringcalling through said 'cut-OH? relay to maintain the same operated, and aretardation-coil in said auxiliary path tovprevent the passage thereoverof the ringing-cu-rrent, substantially as described.

6.` In a telephone system, the combination Withfa telephone-line, of aconnection-terminal normally disconnected therefrom, a relay -forconnecting said connection-terminal with the line, a central source ofcurrent adapted to Vbe connected in the metallic circuit for talkingpurposes', means for operating said relay from said source whenconnection is made with the line by current flowing over a pathincluding a portion of the talking-circuit, means for sending aealling-currentover the line of the called subscriber only andl at thesame time maintaining said relay in operated condition from said'source, and means for preventing thel shortfcircuiting of the ringingcurrent through said source, substantially as described;-

H7. The combination withatelephone-line, of a'connection-terminalnormally disconnected therefrom, -a relay for connecting saidconnection-terminal with the line,a charging source ofv electricity,`acalling source of electricity, saidcharg'ing source'being adapted toenergiZe-said relay when-connection is made with the line, aringing-key'for connecting said calling` source with the line ofa calledsubscriber and for disconnecting the normal path for current from saidcharging source, an auxilia'ry vpath for current from said charging i ii Y Y source completed by the ringing-key during calling, and aretardation-coil in said auxiliary path, substantially as described.

8. =In a-telephonesystem, the combination with a telephone-line', of aline-signal therefor, a cut-olf relay bridged between `the lineconductors and adapted when actuated to render the line-signalinoperative, a cord-circuit to establish connections with the line, asource of steady current connected withthe cord-circuit and adaptedduring a connection to furnish current over thetalking-circuit for theoperation of said cut-off relay and for conversational purposes, aringing-generator adapted to be connected with one side of thecord-circuit to call the wanted subscriber, an auxiliary path forcurrent from said source adapted to be connected with the other side ofthe cordcircuit during calling, the cord-circuit itself being at thistime severed, a retardation-coil in said auxiliary path to prevent thepassage thereover of the ringing-current and to conne it to the calledline entirely, substantially as described. f Y

9. In a telephone system, the combination with a telephone-line, of aline-signal'operated by current from the central oice when thesubscriber is calling, a magnet to render said signalinoperative when aconnection is established with the line for conversation, a centralsource of current adapted to be connected in the line for talking, saidmagnet being operated. from said source during a connection by currentover a portion of the talking-circuit, a calling-generator for sendingringingcurrent over the line of thel called subscriber only, means forsimultaneously sending continuous current through said magnet tomaintain the same actuated during calling, and a retardation-coil in thepath of the latter current to prevent the passage thereover of theringing-current, substantially as described.

10. The combination with a telephone-line, of a charging source ofcontinuous current to furnish current for talking, Va line-signal, amagnet adapted to be energized from said source to render the saidsignal inoperative, the magnet-circuit including a portion of thetalking-circuit, a calling-generator, means to connect said generatorwith the line' and to open the circuit of said source through saidmagnet, means for temporarily sending'continuous current through saidmagnet during ringing to maintain the same actuated, Vandalretardation-coil included lin the path of said temporaryv current toprevent the passage thereover of the ringing-current,substantially asdescribed. i L

ll. The combination with a telephone-line, ofa charging source ofcontinuous current to furnish current over the line for talking, aline-signal, a magnet adapted to be energized IOO from said sourceduring a connection to render said 'signal inoperative, a cord-circuitto establish connections with the line for talking, a calling-generator,means to connect said generator with the line and to open `thecordcircuit, means for temporarily sending continuous current throughsaid magnet during ringingv to maintain the'same operated, and aretardation-coilA included in the path of said temporary current toprevent the passage thereover of the ringing-current, substantially asdescribed.

12. The combination with a telephone-line, of a charging source ofcontinuous current, a magnet adapted to be energized by said chargingsource when connection is made with the line, a calling-generator,aringing-key adapted to connect said calling-generator with the line andto open circuit through said magnet, means controlled by the ringing-keyfor tcmporarily sending a continuous current through i said magnetduring the'time the calling-generator is connected with the line, and aretardation-coil in the path of said temporary current to prevent thepassage thereover ofthe ringing-current, substantially as described.

13. rlhe combination with atelephone-line, of a relay associatedtherewith, a cord connector for uniting said line with anothertelephone-line, a charging source of continuous current adapted to beconnected with said line to send current through said relay, acalling-generator adapted to produce a noncontinuous current, aringing-key adapted to connect said calling-generator with the line andto open the circuit of said charging source through said relay, meansfor temporarily sending a continuous current through said relay toenergize the same during the timeI the calling-generator is in circuit,and a retardation-coil included in the path of said latter current toprevent the passage thereerator with the line and to open the circuitofsaid charging source through said relay and means for temporarilysending a continuous current through said relay during the time thecalling-generator is connected in circuit, and a retardation-coilincluded in the path of said temporary continuous current, substantiallyas described.

15. The combination with a telephone-line, of a relay in a bridgebetween the two limbs of said line, a charging source of electricityadapted when4 connection is made with the line to energize said relay, acalling-generator, a ringing-key adapted to connect saidcallinggenerator with the line and to open the circuit of said chargingsource through said reand a retardation-coil included in the path oflay, means to temporarily `send continuous current through saidbridgedrelay during ringing by the actuation of said ringing-key,

said latter temporary current to prevent the passage of ringing-current,substantially as described.

16. The combination with a telephone-line,

of a relay associated therewith, a cord connector for uniting said linewith another telephone-line, a charging source of continuous currentadapted to be connected with said cord connector through said relay andfurnishing current for talking purposes, a calling-generator adapted toproduce a non-continuous current, a ringing-key adapted to connect saidcalling-generator with the line and to open the circuit of said chargingsource through said relay, means for temporarily sending a continuouscurrent through said relay to energize the same during the time thecalling-generator is in circuit, and a retardation-coil included in thepath of said latter temporary current to prevent the passage of theringing-current, substantially as described.

17. The combination with a telephone-line, of a line-signal therefor, amagnet to render said line-signal inoperative during a connection, asource of current connected with the line during a connection toenergize said magnet over a path including a portion of thetalking-circuit and to furnish current for talking purposes, acalling-generator, a ringing-key adapted to connect saidcalling-generator with the line and to open the circuit of said chargingsource through said magnet, means actuated by` said ringing-key fortemporarily sending a continuous current through said magnet during thetime the calling-generator is connected with the line, and aretardation-coil included in the path of said latter temporary current,substantially as described.

1,8. The combination with a telephone-line,

of a line-signal therefor, a cut-off relay for the 4said relay toenergize the same during the time the calling-generator is in circuit,and a retardation-coil in the path of said temporary current to preventthe passage of the ringingcurrent, substantially as described.

19. The combination with a telephone-line, of a connection-terminalnormally disconnected therefrom, a line-signal, a relay for connectingsaid connection-terminal with the line and for simultaneously renderingsaid signal inoperative, a charging source of continuous current adaptedto energize said relay and to furnish current for talking during aconnection, a calling-generator adapted to produce a non-continuouscurrent, a ringing-key to connect said calling-generator with the lineand to IOO IIO

open the circuit of said charging source through said relay, means fortemporarily sending a continuous current through said relay during thetime the calling-generator is connected in circuit, a retardation-coilincluded in the path of the'latter temporary current for the purpose ofpreventing the passage over said path of the ringing-current,substantially as described.

20. In a telephone system, the combination with a telephone-line, of aline-signaling device therefor', a cut-off relay for the line adaptedwhen actuated to render said line-signaling device inoperative, acord-circuit to establish connection with the line, a steady currentsource associated with said cord-circuit and adapted during a connectionto furnish current over a portion of the talking-circuit for theoperation of said relay and over the line for talking, aringing-generator adapted to be connected with the line to call asubscriber located thereon, means to open the cord-circuit duringcalling to prevent the ringing-current from flowing' back over the same,means for temporarily sending a continuous current through said cut-offrelay during calling, and means connected in the path of said temporarycurrent to permit the passage of the continuous current and to preventthe passage of the ringing-current, substantially as described.

21. In a telephone system, the combination with a telephone-line, of aline-signaling device therefor, a cut-Ol relay for the line adapted whenactuated to render said line-signaling device inoperative, acord-circuit to establish connections with the line, a steady currentsource associated with said cord-circuit and adapted during a connectionto furnish current over a portion of the talking-circuit for theoperation of said cut-off relay and over the line for talking, aringing-generator adapted to be connected with the line to call thesubscriber located thereon, means to open the cord-circuit duringcalling to prevent the ringing-current from flowing back over the same,means for temporarily sending a continuous current through said relayduring calling, and a retardatione'coil in the path of said lattercurrent to prevent the passage of ringing-current and to permit thepassage of steady current, substantially as described.

22. In a telephone system, the combination with atelephone-line, of aline-signal therefor, a cut-off relay bridged between the lineconductors and adapted when actuated to render the line-signalinoperative, a cord-circuit to establish connections with the line, asource of steady current bridged across the cord-circuit and adaptedduring the connection to furnish current for the operation of the cut-orelay, a ringing-generator adapted to be connected with the cord-circuitto call the wanted subscriber, the cord-circuit being opened betweensaid source and the cut-off relay at the time of calling the subscriber,means for temporarily sending a continuous current through said cut-offrelay during calling to maintain the same operated, and aretardationcoil in the path of said temporary current to prevent thepassage thereover of the ringingcurrent, substantially as described.

4 23. In a telephone system, the combination with a telephone-line, of aconnection-terminal normally disconnected therefrom, a relay forconnecting said terminal with the line, a central source of currentadapted to be connected in the metallic circuit for talking purposes,means for operating said relay from said source when connection is madewith the line by current flowing over a path including a portion of thetalking-circuit, a calling-generator for sending ringingcurrent over theline of the called subscriber only, means for simultaneousl y sendingcontinuous current through said relay to maintain the same actuatedduring calling, and a retardation-coil in the path of the latter currentto prevent the passage thereover of the ringing-current, substantiallyas described.

24. In a telephone system, the combination with a telephone-line, of amagnet connected with the talking-circuit thereof, a cord-circuit, acalling-generator, a ringing-key to connect said generator with thecord-circuit to call the subscriber upon the line, said key serving toopen the cord-circuit during ringing, and a source of steady current anda retardation-coil in series therewith temporarily connected with thecord-circuit by said key in calling to maintain said magnet operated,the said retardation-coil serving to oppose the passage of theringing-current, substantially as described. v

25. In a telephone system, the combination with a telephone-line, of aline-signal, a relay to render said signal inoperative when a connectionexists, a cord-circuit, a source of current associated therewith andconnected with the line during a connection to furnish current fortalking and for the operation of said relay, the relay-circuit includingone talking-strand of the cord-circuit and a portion of one side of theline with suitable return, a ringing-generator, a key to open the saidrelay-circuit when operated and to connect the said generator in thecircuit of the line, means also actuated by said key for temporarilysending a continuous current through said relay during ringing, and aretardation-coil in the said temporary path so formed by theringing-key, substantially as described.

26. In a telephone system, the combination with a telephone-line, of aline-signaling device therefor, a cut-off magnet for the line adaptedwhen actuated to render said line-signaling device inoperative, acord-circuit to establish connections with the line, a steady-currentsource associated with said cord-circuit and adapted during a connectionto furnish current over a portion of the talking-circuit for the opera-IOO IIO

I SO

said generator with the cord-circuit and line to call the Wantedsubscriber, said switch serving to open the cord-circuit duringcallingto prevent the ringing-current from ilowing back over the sameand disturbing the calling subscriber, an auxiliary path for currentcompleted by said key-switch from said source through said cut-offmagnet during calling, `and a retardation-coil in said auxiliary path ato prevent the passage ofthe ringing-current, `substantially asdescribed. 27. In a telephone system, the combination With amultiple-switchboard common-battery telephone-line having itsswitchboard-section normally disconnected from the external linetweenthe strands of the cord-circuit and adapted to send current through saidrelay to `actuate the same during a connection and to erator, aringing-key in the cord-circuit bei tween the connection of the saidbattery there- With and the connecting-plug, said key serving whenactuated to open the cord-circuit strands and thus disconnect saidbattery, said key serving at the same time to connect said generatorbetween ground and one side of the telephone-line, to actuate thesubscribers bell, an auxiliary path for current completed from the livepole of said battery to the other side of the line by said key duringringing Whereby current from said battery flows over said auxiliary paththrough said bridgedcut-oif i relay and the grounded ringing-generatorto maintain the same actuated during ringing, and a retardation-coilincluded in said auxiliary path to prevent the passage of theringing-current thereover and coniine it to the subscribers line,substantially as described.

28. In a telephonesystem, the combination with a telephone-line, of aline-signal therefor, a magnet torender said signal inoperative during aconnection, a ringing-generator and a source of steady current connectedwith the line When calling the Wanted subscriber,` the current from saidsteady-current source serving to maintain said magnet operated duringringing and having its path completed through said ringing-generator,substantially as described.

29. In a telephone-system, the combination witha telephone-line, of aline-signal therefor, a magnet to render said signal inoperative duringa connection', a ringing-generator, and a source of steady currentconnected with the line when calling the Wanted subscriber, the

current from said steady-current source serving to maintain said magnetoperated during ringing and having its path completed through saidringing-generator, and means to prevent the ringing-generator currentfrom being confined to the path of the steady-current source,substantially as described.

30. In a telephone system, the combination With a telephone-line, of aline-signal therefor, a magnet to render said signal inoperative duringa connection, a ringing-generator, and a source of steady currentconnected With the line when calling the wanted subscriber, the currentfrom said steady-current source serving to maintain said magnet operatedduring ringing and having its path completed through saidringing-generator, and a retardation-coil in said steady-current pathout of the desired path of the ringing-current to prevent the latterfrom flowing thereover, substantially as described.

31. The combination with a telephone-line, of a signal therefor, amagnet to render said signal inoperative during a connection, a batteryand a ringing-generator 'connected with said line When calling thesubscriber, the battery and ringing-generator having derived circuits,the said generator being in the com- Irion portion thereof and the s aidbattery serving to maintain said magnet operated during ringing,substantially as described.

32. In a telephone signaling system, amainline circuit, anon-continuous-current generator for ringing the substation, acontinuouscurrent generator, means for connecting both to the main-linecircuit simultaneously and by the same operation to call the Wantedsubscriber, a line-signal, an electromagnet connected With said circuitto render said signal inoperative during a connection, said magnet beingenergized by said continuous-current generator during ringing and over apath of loW actual resistance but relatively high apparent resistance,substantially as described.

33. In an electric signaling system, a main circuit,anon-continuous-current generator for calling the substation, acontinuous-current generator, means for connecting both to the saidcircuit simultaneously and by the same operation when it is desired tocall the subscriber, a line-signal, an electromagnet in a IOO IIO

branch of said circuit and adapted to be enering a main circuit, aline-signal connected therewith, an electromagnet connected with theline to render said signal inoperative, an alternating-current generatorfor sending outgoing signals, a continuous or uniform-direction currentgenerator and a retardation-coil, and a signal-sending key or circuitcontroller interposed between the main circuit and both generators andadapted when operated to close the circuit of both over the said circuitsimultaneously.

35. In a telephone signaling system, a main circuit, a ringing-currentgenerator and a continuous-current generator associated together at thecentral station of the said circuit, a circuit-closer for connectingboth to the said main circuit simultaneously and by the same operation,means for disconnecting both at the end of the call without taking downthe connection, a polarized electromagnetic bell at the substationresponsive to alternating current only andv adapted to give a signalupon the operation of said circuit-closer, a line-signal, anelectromagnet to render said signal inoperative during a connection andactuated by current from said continuous-current generator, and means toprevent the passage of ringing-current over said lcontinuous-currentpath, substantially as described.

36. The combination with a main circuit, of a line-signal therefor, andan electromagnet to render said signal inoperative during connectionand` connected with the main circuit, a source of alternating currentfor sending outgoing ringing-currents over the circuit, a source ofcontinuous current for actuating said electromagnet to render the saidsignal inoperative during ringing and having impedance in its path toprevent the passage of the ringing-current, and means for connectingboth sources with the circuit simultaneously in the normal act ofcalling the wanted subscriber, substantially as described.

37. The combination with a main circuit, of a polarized electromagneticcall device included therein responsive to alternating currents, analternating-current generator, a continuous-current generator andretardation-coil associated therewith, a signal at the same station asthe said generators, an electromagnet connected with the said circuit torender said signal inoperative during a connection, and a compoundcircuit-closing device controlling the terminals'of both generators andtheir connections with the main circuit so that when operated in callinga subscriber to make such connections the said magnet will be operatedby the continuous current to prevent the operation of said signal by thealternating current and the latter current will be confined to thedesired path, substantially as described.

38. In an electric signaling system, the combination with a maincircuit, a line-signal, a cut-off relay connected with talking-circuitand adapted to render said signal inoperative during a connection, analternating-current generator, a relatively low resistancecontinuous-current generator to operate said relay during ringing, acircuit-closer controlling branch terminals of the said main circuit andalso the terminals of both generators and adapted when operated toconnect both with said main circuit, an electromagnetic resistance orretardation coil of low actual but high inductive resistance included inthe circuit of the continuous generator to prevent the currents of thealternating generator from being short-circuited or shunted through thesaid continuous-current generator while offering little opposition tothe continuous currents developed thereby.

Signed by me at Chicago, county of Cook, State of Illinois, this 28thday of November, 1902.

ALBION D. T. LIBBY.

Witnesses:

C. S. WINsToN, ROBERT LEWIS AMES.

